More precisely, the invention relates to a medium- or high-tension circuit breaker having abutting arcing contacts and comprising a casing filled with gas having good dielectric properties containing a stationary first abutting contact connected to a first current terminal, and moving equipment comprising a first tube capable of being displaced by a drive rod, said first tube being connected to a second current terminal, and co-operating with a second tube to define a blast volume and extended by a blast nozzle, said circuit breaker further including a semi-moving tubular second abutting contact receiving thrust at an annular end from a first end of a coil spring having its second end bearing against an annular shoulder of the first tube, the annular end of the second contact co-operating by abutment with an annular end of the first tube to open the abutting contacts.
Such circuit breakers with abutting arcing contacts are known in which the arc is blasted by gas being compressed during an opening operation. In those circuit breakers, gas compression takes place before the arcing contacts separate (precompression). During the precompression stage, the main contacts of the circuit breaker are opened, which main contacts may be disposed outside the casing. Such a circuit breaker is described in French Patent No. 2,661,549 and corresponding U.S. Pat. No. 5,162,627.
In those circuit breakers, with increasing short circuit currents, there appear high repulsive forces between the abutting contacts which thus tend to move apart, and which are thus rapidly damaged by arcing. To avoid this phenomenon, it is necessary to use a coil spring having a large compression force to withstand the repulsive forces. Unfortunately, this force acts on all of the moving parts of the apparatus constituted by the circuit breaker and its control mechanism, thus requiring equipment that is heavy and expensive.
The present invention seeks to solve this problem of repulsion between abutting contacts without increasing the compression force of the spring. In addition, because of the invention, the main contacts are integrated in the circuit breaker in a disposition that is simple and compact.